Determination of the boundaries between fractions and extraction of selected fractions in a fractionated sample

ABSTRACT

An apparatus and method are provided for determining boundaries between fractions in a fractionated sample. The method includes the steps of providing the fractionated sample in a receptacle, the receptacle having a transparent window, positioning the receptacle in a known position relative to datum means, capturing an image of the receptacle and datun means, and processing the image to determine the position of boundaries between the fractions in the sample relative to the datum means. An apparatus and method for extracting a selected fraction of a fractionated sample are also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus forautomatically determining the boundaries between fractions in afractionated sample and to a method and apparatus for automaticallyextracting fractions from a fractionated sample and in particular tosuch a method and apparatus wherein the fractionated sample is afractionated blood sample.

Blood samples are often analysed or processed by fractionation toseparate particular components. This allows particular components ofinterest to be extracted from a sample. Fractionation is achieved bycentrifugation of the sample, which results in a sample having a numberof layers or fractions, each fraction consisting of particularcomponents of the blood. Typically, the centrifuged sample comprisesthree fractions, the uppermost fraction containing (amongst othercomponents) plasma, the lowermost fraction containing (amongst othercomponents) red blood cells and the middle fraction, known as the ‘buffycoat’, containing (amongst other components) white blood cells.

The fractions are typically extracted in turn by a pipette means undermanual control. The fraction containing the component of interest isretained and the other fractions may be retained or disposed of asdesired. Manually controlled extraction in this manner is time consumingand expensive. It is also requires considerable skill as, to the nakedeye, the boundaries between fractions can be difficult to distinguish.These problems are exacerbated if the ‘buffy coat’ is the fraction ofinterest, for instance if DNA analysis of the sample is required, as thebuffy coat is typically relatively thin in relation to the otherfractions.

It is therefore an object of the present invention to provide a methodand apparatus for automating some or all of this process.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amethod of determining the boundaries between fractions in a fractionatedsample, the method comprising the steps of: providing the fractionatedsample in a receptacle, the receptacle having at least a transparentwindow; providing a datum means; positioning the receptacle in a knownposition relative to the datum means; capturing an image of thereceptacle and datum means; and processing the image to determine theposition of boundaries between the fractions in the sample relative tothe datum means.

This thus provides an automatic method for determining the position ofthe boundaries between fractions within a sample. Once the boundariesare determined automatically, extraction of fractions of interest canalso be carried out automatically.

The image capture may be carried out by a digital imaging means, such asa digital camera.

The digital image is preferably processed using an edge detectionalgorithm to determine the position of the boundaries between fractions.

If a receptacle of known dimensions is used, the processing may furtherinclude the step of calculating the volume of each fraction.

The receptacle may be illuminated by white, coloured or filtered lightin order to improve the quality of the captured image or the contrastbetween fractions. In particular, red light may be used. Additionally oralternatively, the image may be captured through a filter, if desired,to improve the contrast between fractions.

The datum means is preferably a datum plate upon which the receptaclemay be positioned. The datum plate may be movable between an operationalposition and a stowed position. The digital imaging means is preferablymounted in a fixed relation to the operational position of the datumplate.

In use, a receptacle is held at a known orientation and positioned onthe datum plate when the datum plate is in the operational position.This allows the position of the lower end of the receptacle to bedetermined and hence the relative positions of the fraction boundariesin the sample to be determined.

A calibration means may be provided on the datum plate if desired. Thecalibration means may be provided with suitable markings or formationsto allow any or all of the focus, colour, contrast or brightness levelsor alignment of the imaging means to be determined and adjusted.

Preferably, the method further comprises the additional step ofextracting a selected fraction or fractions of interest from the sample.Extraction is preferably achieved by a pipette means. The pipette meansis preferably inserted into a selected fraction and operated so as toaspirate a volume substantially equal to the volume of the selectedfraction.

Preferably, the fractions are aspirated in order starting with theuppermost fraction. If the fraction of interest is not the uppermostfraction, then once the uppermost fraction is aspirated it may bediscarded and the next fraction then aspirated. Once the fraction ofinterest is aspirated, it may be dispensed into another receptacle forstorage or analysis.

As the fraction boundaries may be intermingled, it may be desirable toextract a volume of material equal to a volume slightly larger orslightly smaller than the fraction providing the maximum amount of thecomponent of interest or the maximum concentration of the component ofinterest respectively.

The receptacle is preferably a test tube of known dimensions, such as afalcon™ tube. A processing means is preferably provided for determiningthe positions of the fraction boundaries and calculating the volume ofeach fraction. The processing means may additionally control the pipettemeans.

According to a second aspect of the present invention there is provideda method of extracting a selected fraction of a fractionated sample, themethod comprising the following steps: providing the fractionated samplein a receptacle, the receptacle having at least a transparent window;providing a datum means; positioning the receptacle in a known positionrelative to the datum means; capturing an image of the receptacle anddatum means; processing the image to determine the position ofboundaries between the fractions in the sample relative to the datummeans; calculating the volume of each fraction in the receptacle fromthe determined positions of the boundaries between the fractions and thedimensions of the receptacle; inserting a pipette means into theselected fraction and operating the pipette means so as to aspirate avolume substantially equal to the calculated volume of the selectedfraction.

The second aspect of the invention may incorporate any or all of thefeatures described in relation to the first aspect of the presentinvention as appropriate or as desired.

According to a third aspect of the present invention there is providedan apparatus suitable for determining the boundaries between fractionsin a fractionated sample, the apparatus comprising: a receptacle forholding a fractionated sample, the receptacle having at least atransparent window; a datum means; positioning means for positioning thereceptacle in a known position relative to the datum means; imagingmeans for capturing a image of the receptacle and datum means; andprocessing means for processing the image to determine the position ofthe fraction boundaries relative to the datum means.

According to a fourth aspect of the present invention there is providedan apparatus suitable for extracting a selected fraction of afractionated sample, the apparatus comprising: a receptacle for holdinga fractionated sample, the receptacle having at least a transparentwindow; a datum means; positioning means for positioning the receptaclein a known position relative to the datum means; imaging means forcapturing a image of the receptacle and datum means; and processingmeans for processing the image to determine the position of the fractionboundaries relative to the datum means and for calculating the volume ofeach fraction of a fractionated sample from the determined positions ofthe boundaries between the fractions and the dimensions of thereceptacle.

The apparatus according to the third or fourth aspects of the inventionmay incorporate means relating to any or all of the features describedin relation to the methods of the first aspect or second aspects of thepresent invention as appropriate or as desired.

The apparatus may include automated robotic apparatus to achieve fullautomation of the process.

Preferably the above method and apparatus is adapted for determining theboundaries between fractions in a fractionated sample and extractingdesired fractions from the fractionated sample in the case wherein thesample is a fractionated blood sample. In particular this method andapparatus may be applied to extracting the buffy coat fraction from afractionated blood sample. It is of course possible to apply thistechnique to the determination of boundaries between fractions and theextraction of fractions in other types of fractionated sample.

The skilled man will of course appreciate that the above method andapparatus may be adapted to allow a plurality of samples to be processedat any one time.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention is more clearly understood, one embodimentwill now be described in greater detail below, with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic diagram showing a fractionated blood sample in atest tube and features of an apparatus for identifying and extractingdesired fractions of the sample;

FIG. 2 is a schematic diagram of features of an apparatus foridentifying and extracting desired fractions from a plurality ofsamples; and

FIG. 3 is a schematic block diagram of the control circuitry for such anapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a fractionated blood sample is provided in atest tube 10. The sample has three fractions, an uppermost or ‘plasma’fraction 12, a lowermost or ‘red blood cell’ fraction 16 and anintermediate or ‘buffy coat’ fraction 14, which contains white bloodcells.

The test tube 10 of this embodiment is entirely transparent such thatthe entire test tube acts as a viewing window. As an alternative, thetest tube 10 could have a portion of the tube acting as a viewingwindow. The window need not be 100% transparent but may be partiallytransparent.

In order to determine the position of the fraction boundaries, the testtube 10 is held vertically and positioned with its lower end in contactwith a datum plate 18. An image of the test tube 10 is then captured bydigital camera 20. The image is then processed by a suitable processingmeans 100 to determine the positions of the fraction boundaries relativeto the datum plate 18. The processing means 100 typically achieves thisby use of edge detection algorithms.

In order that a better quality image can be captured the test tube 10may be illuminated by white, coloured or filtered light as required. Acalibration means 24 may be provided adjacent to the test tube 10. Thecalibration means 24 may be provided with suitable markings to allow thefocus, colour, brightness or contrast levels or alignment of camera 20to be adjusted. A filter 36 may be provided to improve the contrastbetween fractions in the sample.

The test tube 10 is of known dimensions. Thus from the determinedposition of each fraction boundary, the volume of each fraction can becalculated by the processing means 100. The processing means may thencontrol an automatic pipette means 22. The pipette means can be insertedinto the sample to a desired position and used to aspirate a volumeequal to the calculated volume of a particular fraction. Typically, thefractions are aspirated in turn starting with the uppermost. Thosefractions which are not of particular interest may be discarded afteraspiration and those fractions which are of further interest may bedispensed into other receptacles for storage or analysis.

As an example, if it is desired to extract the buffy coat 14 for furtheranalysis, the pipette means is used to aspirate the plasma fraction 12to a level just above the upper boundary of the buffy coat 14. Theaspirated plasma fraction 12 is then discarded. The pipette means isthen used to aspirate the buffy coat 14 to a level just below the lowerboundary of the buffy coat 14. The buffy coat 14 material in the pipettemeans 22 may then be transferred to a further receptacle for storage oranalysis.

It is of course possible that if a more concentrated sample of buffycoat fraction 14 is required, the plasma fraction 12 can be aspirated toa level just below the upper boundary of the buffy coat 14 andsubsequently, the buffy coat fraction 14 can be aspirated to a leveljust above the lower boundary of the buffy coat 14. In a furtheralternative, it is possible that the buffy coat fraction 14 may beextracted in a single operation by positioning the tip of the pipettemeans 22 either just above or just below the lower boundary of the buffycoat fraction 14 as desired and aspirating a volume of material equal tothe volume of the buffy coat fraction 14.

FIG. 2 illustrates schematically how this method and apparatus may beapplied to process a plurality of fractionated samples. In FIG. 2, aplurality of samples are each retained in test tubes 10. The test tubes10 are held in a tube rack 30. The tube rack 30 may optionally beprovided with releasable rack clamps 32 to further secure the test tubes30.

Back light 44 illuminates an optical booth 42 with white, coloured orfiltered light as required. Back light 44 is used generally toilluminate the top level of the samples and the orientation of the testtubes 10. Light 34 is provided above the samples and is used to identifythe buffy coat fraction 14.

A tube pop-up actuator 28 may be used to raise one or more tubes 10 intoa position whereby the tube can be gripped by tube gripping means 26.This is facilitated by utilization of an X-Y table 40 enabling theplurality of tubes to be positioned suitably corresponding to theactuator 28. The tube gripping means has gripper jaws 38 ensuringvertical compliance of the tubes 10. The tube gripping means 26 is thenoperable to position the tubes 10 on the datum plate 18. The gripperjaws 38 enable the tubes 10 to be held securely until reaching the datumplate 18 at which point they are able to rest on the datum plate 18. Thedatum plate 18 may itself be movable from a stowed position to anoperational position to facilitate the movement of the tubes 10 by thetube gripping means 26 into position on the datum means 18. After thefraction boundaries are determined and any desired fractions areextracted, the tube gripping means 26 is operable to either return thetubes 10 to their original rack 30 or to place the tubes 10 in adifferent tube rack 30. The tube gripping means 26 is moved between therequired positions by an actuator (not shown).

In the case wherein more than one tube 10 is selected from the rack, thetubes 10 may be imaged and have their fractions extracted simultaneouslyor in turn. If the imaging is to be carried out simultaneously eitherindividual cameras 20 may be provided for each tube or alternatively onecamera may be provided for imaging a plurality of tubes. Additionally,if fractions in a plurality of tubes 10 are to be extractedsimultaneously the pipette means 22 is provided with a plurality ofpipette heads, each pipette head being individually controllable. Thisallows the pipette heads to extract the correct amount of material fromeach test tube 10.

FIG. 3 shows how the various components of the apparatus may beconnected. The processing means 100 is connected directly to the camera20, the pipette means 22, the tube gripping means 26, the pop-upactuators 28 and to datum plate moving means 118. The processing meansmay also be provided with a user interface 102. The processing means mayalso be connected to means 110 for controlling the illumination of thetubes 10 during image capture. In one preferred embodiment, theprocessing means and user interface may be provided by a computer orcomputer system.

It is of course to be understood that the invention is not to be limitedto the details of the above embodiment, which is described by way ofexample only. Many variations are possible within the scope of thefollowing claims.

1. A method of determining boundaries between fractions in afractionated sample, the method comprising the steps of: providing thefractionated sample in a receptacle, the receptacle having at least atransparent window; providing a datum means; positioning the receptaclein a known position relative to the datum means; capturing an image ofthe receptacle and datum means; and processing the image to determinethe position of boundaries between the fractions in the sample relativeto the datum means.
 2. The method of claim 1, wherein the step ofcapturing an image includes using a digital imaging means.
 3. The methodof claim 2, wherein the step of processing the image includes using anedge detection algorithm to determine the position of the boundariesbetween the fractions.
 4. The method of claim 3, wherein the step ofprocessing the image further comprises a step of calculating the volumeof each fraction.
 5. The method of claim 1, further comprising a step ofilluminating the receptacle by white, coloured or filtered light,thereby to improve the quality of the captured image or the contrastbetween fractions.
 6. The method of claim 1, wherein the step ofcapturing an image includes capturing the image through a filter therebyto improve the contrast between fractions.
 7. The method of claim 1,wherein the datum means is a datum plate upon which the receptacle ispositioned and the datum plate is moveable between an operationalposition and a stowed position.
 8. The method of claim 2, wherein thedatum means is a datum plate upon which the receptacle is positioned andthe datum plate is moveable between an operational position and a stowedposition and the digital imaging means is mounted in a fixed relation tothe operational position of the datum plate.
 9. The method of claim 7,wherein the step of positioning the receptacle includes holding thereceptacle at a known orientation and position on the datum plate whilethe datum plate is in the operational position thereby enabling theposition of the lower end of the receptacle to be determined and therelative positions of the fraction boundaries in the sample to bedetermined.
 10. The method of claim 7, further comprising a step ofproviding a calibration means on the datum plate.
 11. The method ofclaim 10, wherein the calibration means has markings or formations toallow any or all of the focus, colour, contrast or brightness levels oralignment of the imaging means to be determined and adjusted.
 12. Themethod of claim 1, further comprising a step of extracting a selectedfraction or fractions of interest from the sample.
 13. The method ofclaim 12, wherein the step of extraction is achieved by using pipettemeans and the pipette means is inserted into a selected fraction andoperated so as to aspirate a volume substantially equal to the volume ofthe selected fraction.
 14. The method of claim 13, wherein the fractionsare aspirated in order starting with the uppermost fraction and thefractions are aspirated and then discarded until a fraction of interestis aspirated, which is dispensed into another receptacle.
 15. The methodof claim 13, wherein the step of processing the image further comprisesproviding a processing means to determine the positions of the fractionboundaries and calculating the volume of each fraction, and controllingthe pipette means using the processing means.
 16. A method of extractinga selected fraction of a fractionated sample, comprising: providing thefractionated sample in a receptacle, the receptacle having at least atransparent window; providing a datum means; positioning the receptaclein a known position relative to the datum means; capturing an image ofthe receptacle and datum means; processing the image to determine theposition of boundaries between the fractions in the sample relative tothe datum means; calculating the volume of each fraction in thereceptacle from the determined positions of the boundaries between thefractions and the dimensions of the receptacle; and inserting a pipettemeans into the selected fraction and operating the pipette means so asto aspirate a volume substantially equal to the calculated volume of theselected fraction.
 17. An apparatus for determining the boundariesbetween fractions in a fractionated sample, comprising: a receptacle forholding a fractionated sample, the receptacle having at least atransparent window; a datum means; positioning means for positioning thereceptacle in a known position relative to the datum means; imagingmeans for capturing an image of the receptacle and datum means; andprocessing means for processing the image to determine the position ofthe fraction boundaries relative to the datum means.
 18. The apparatusof claim 17, wherein the imaging means is a digital imaging means. 19.The apparatus of claim 17, wherein the processing means uses an edgedetection algorithm to determine the position of the fraction boundariesin a fractionated sample.
 20. The apparatus of claim 17, wherein theprocessing means is operative to calculate the volume of each fractionin a fractionated sample.
 21. The apparatus of claim 17, furthercomprising a light provided at a position so as to illuminate thereceptacle with white, coloured or filtered light.
 22. The apparatus ofclaim 17, further comprising a filter provided between the receptacleand the imaging means to improve contrast between fractions in afractionated sample.
 23. The apparatus of claim 17, wherein the datummeans is a datum plate.
 24. The apparatus of claim 23, wherein acalibration means is provided on the datum plate.
 25. The apparatus ofclaim 24, wherein the calibration means has markings or formations toallow any or all of the focus, colour, contrast or brightness levels oralignment of the imaging means to be determined and adjusted.
 26. Theapparatus of claim 17, further comprising pipette means operative toaspirate a chosen volume of the selected fraction.
 27. The apparatus ofclaim 26, wherein the pipette means is operative to aspirate a volumesubstantially equal to the calculated volume of the selected fraction.28. The apparatus of claim 26, wherein the processing means is operativeto control the pipette means.
 29. The apparatus of claim 17, wherein theapparatus includes automated robotic apparatus.
 30. Use of the apparatusof claim 17 in determining the boundaries between fractions in afractionated sample.
 31. An apparatus for extracting a selected fractionof a fractionated sample, comprising: a receptacle for holding afractionated sample, the receptacle having a transparent window; a datummeans; positioning means for positioning the receptacle in a knownposition relative to the datum means; imaging means for capturing animage of the receptacle and datum means; and processing means forprocessing the image to determine the position of the fractionboundaries relative to the datum means and for calculating the volume ofeach fraction of a fractionated sample from the determined positions ofthe boundaries between the fractions and the dimensions of thereceptacle.
 32. The apparatus of claim 30, further comprising pipettemeans operative to aspirate a chosen volume of the selected fraction.33. The apparatus of claim 31, wherein the pipette means is operative toaspirate a volume substantially equal to the calculated volume of theselected fraction.
 34. The apparatus of claim 31, wherein the processingmeans is operative to control the pipette means.
 35. The apparatus ofclaim 30, wherein the apparatus includes automated robotic apparatus.36. Use of the apparatus of claim 30 in extracting a selected fractionof a fractionated sample.